A variety of damper constructions employing the use of rubber or other elastomeric material of a constant dynamic spring rate (hereinafter referred to as "k value") to insulate the communication of energy between substantially metallic masses, have been proposed, either for the absorption of vibration in for example, automobiles, trucks and their constituent components, or, for the isolation of vibration which arises in one component from reaching another, in for example the constituent elements of automobiles, trucks, and industrial machinery.
With regard to the former construction of dampers, adapted to absorb vibration, one common structure proposed comprises an inertial mass communicating through rubber or other elastomeric material with a relatively more massive vibrating article. For example, U.S. Pat. No. 2,271,935 relates to means for reducing the energy of a travelling or standing wave occuring in cables in overhead spans where high concentrations of stress and reversals of stress are focused at the ends of the cable comprising points of reflection of the wave. An inertial weight communicating through rubber material with an arm connected to the cable, thereby having its centre of gravity laterally eccentric from the axis of the cable, converts the vertical energy of either travelling or standing waves occuring in the cable into tortional or twisting oscillations with respect to the axis of the cable, which by reason of friction between strands of the cable caused by such twisting thereby dissipates energy along the length of the cable. Further, the rubber material communicating between the inertial weight and the arm connected to the cable resiliently constrains the oscillatory motion of the arm due to the inertia of the weight, thereby dampening the wave energy occuring in the cable.
In another example, U.S. Pat. No. 3,663,002 relates to means for dampening vibration induced body noise in an automobile. An inertial weight, communicating through rubber material with an automobile body at a point rearward of the transmission and over the drive line or propeller shaft, is tuned to vibrate when subjected to a predetermined range of vibrating cycles per second, thereby transferring energy from the automobile body to the inertial weight. The transfer of energy takes place through an insulating connection composed of rubber or other elastomeric material of a constant k value.
Dampers of the type described composed of an inertial mass and an insulating connector which have been proposed in the prior art are only suitable for dampening a specified frequency of vibration and have only minimal effect towards dampening other frequencies to which they are not tuned. This necessitates any manufacturer of automobiles for example, to maintain an inventory of dampers which dampers vibrate at specified frequencies within a specified range.
In each situation, where the vibration may exist over a range of frequencies, individual dampers, each of a different frequency by trial and error must be applied to determine their effectiveness and if unsuitable, removed and returned to inventory. This is particularly so in the case of automobiles where a variety of sources of different frequencies of vibration are present providing interference and omnidirectional vibration. Such sources of vibration may comprise inherent drive live vibrations, gear noise from the differential, an unbalanced drive shaft, transmission gear noise and engine noise, a combination of which sources of vibration may all be magnified through the driveshaft. These same sources of vibration may vary in frequency with vehicle use and climate according to the temperature of such component parts and the temperature of vehicle fluids and lubricants. Additionally, because dampers are constructed in part of elastomeric materials, they do not vibrate at the same frequency under all conditions, and therefore, are not as effective in, for example, winter as in summer.
It is therefore an object of this invention to provide a new vibration damper for absorbing energy causing vibrating noise which overcomes the deficiencies of prior art structures.
Further and other objects of the invention will be realized by those skilled in the art from the following summary, and detailed description of embodiments of the invention.